Mitophagy is a specialized form of macroautophagy responsible for removal of non-functional mitochondria from the cell. Given the prominent role that mitochondria play in oxidative stress, it has been suggested that mitophagy is critical to protein turnover in skeletal muscle. It is currently impossible to determine how each form of autophagy, including mitophagy, contributes to protein turnover. The immediate goal of this application is to develop bioanalytical approaches to determine mitophagy fluxes in cell cultures and skeletal muscle. The main parameter to measure is mitophagy flux (the rate at which mitophagy occurs) using novel technologies based on individual organelle measurements by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) and proteomic profiles. The long-term goal is to apply these bioanalytical approaches to characterize the role of mitophagy in human conditions such as hyperthyroidism and aging that are characterized by alterations in protein turnover. The specific aims of this application are: 1. Define new mitophagy flux analyses based on individual organelle measurements by CE-LIF. 2. Identify organelle-specific proteome changes in abundance, carbonylation and ubiquitination that are associated with changes in mitophagy flux. 3. Determine changes in mitophagy flux in skeletal muscle of hyperthyroid rat, aging rat and aging human models. This work approaches mitophagy from a unique angle, aiming to integrate individual organelle measurements and proteome profiles to define altered mitophagy fluxes with high specificity, even when in the presence of other forms of autophagy. We will the transfer the new technologies to a clinical research setting to investigate mitophagy in human skeletal muscle. Long-term impact of the findings of this work would be the basis for investigating mechanisms of mitophagy and its role in disease and aging.